It’s clear that the Five Guys cannot rest knowing that their robot isn’t perfect.

While Paul had to leave early after having worked since the morning, Matthew, Warren, and Nathan continued their work for over seven hours. At midnight, Chris joined in, and the four collaborated to perfect the fully constructed robot. Burning through the night to tune the rubber-band motor for speed, ensure the trigger for the jaws was fail-safe, and add a robot-repelling bumper, Five Guys Robotics may have been the last to leave the Innovation Gym, but we left the most confident.

The Five Guys are going to meet at 5pm as always, but out of necessity and team consensus, Paul did some independent prototyping this morning on the day before the competition. As previously noted, we don’t have our counter-spring mechanism built yet, which is the part that holds the jaws of our robot open long enough for it to reach the hula hoop, at which point triggers will be tripped by hitting the hula hoop, letting loose the rubber bands that are counteracting the spring mechanism. At that moment, the jaws will close very quickly.

What you see below amounts to two man-hours and about three design iterations. It is our trigger, and it sits between two undercarriage-mounted holders with a 1/2″ dowel running through all three. It will be mounted near the rear of our robot and is basically a grown-up’s rubber band gun. The only consequence of this design is that rubber bands may come shooting out the front of our robot, but we can brand that as a feature rather than an error.

Our robot’s mechanism of action is based upon two rows of “teeth” (cardboard, hand-cut) mounted onto a “spine” (MDF, laser-cut) which is mounted onto two radial mounts each (ABS, 3D printed), and all four of those are affixed to the foam-core ceiling of our robot.

There is no point to meticulous design without meticulous measurement.

Here are the mandibles successfully attached to the undercarriage. Note the foam core spacers that ensure even distribution and reinforce the somewhat weak cardboard.

We cannot overstate the value of brainstorming in our prototyping process.

A lot of work in CAD for what is basically a hook for rubber bands.

What’s left: now with one day remaining, we need to build what we affectionately call the “counter-spring mechanism.” We’ve already built the “spring mechanism,” which entails those small hooks connecting to the spines in a way that makes the natural state of the mechanism closed and up against the ceiling rather than open. The counter-spring, as the name implies, will counteract the closing force of the spring mechanism, and through a trigger that will be sprung by the hula-hoop, the counter-spring will detach, allowing the strong force of the spring to quickly and forcefully close the jaws, in such a way, we assume, that will gather ball-pit balls effectively. We expect the counter-spring to take about four hours of team time, sparing at least two after that for fine tuning our car and testing it exhaustively.

Our car is powered by a parallel, horizontally-opposed 2×2 rubber band engine directly mounted on the rear axle. It delivers outstanding torque for a car in its class. (The duct tape is only to help the glue set)

3D Printers do not know the meaning of “tolerance”. Building moving parts with a 3D printer is an iterative process.

Five Guys have a love-hate relationship with the 3D printers.

This is us (minus Paul, behind the camera) after a very successful test of our drivetrain. Glided right into the center of Caruth and stopped on a dime, all in a few seconds.